THE "IRON BLOW" AT THE LINDA GOLDFIELD. 

 By a. Thiteeau, F.a.S. 



In the recently issued printed Papers and Transactions of 

 the Royal Society of Tasmania, on page 216, are published 

 some notes by Mr. R. M, Johnston, F.L.S., an esteemed 

 member of the Society, on the " Iron Blow " at the Linda 

 Goldfield, his conclusions having been based upon the 

 examination of some rocks and specimens from that locality 

 received from Mr. Grotty and Mr. Belstead, the Secretary for 

 Mines. 



It is upon that remarkable gold-deposit that I desire to 

 offer a few remarks, at the same time embracing the 

 opportunity of supplementing and elaborating my report, No. 

 146 of 1886, presented to Parliament. 



In the following remarks, I shall exclusively confine myself 

 to the question of the probable origin of this unique gold 

 formation in furtherance of my theory of its being due to 

 ** volcanic agency," and not, as Mr. Johnston contends, to 

 local decomposition, especially so far as the dark coloured 

 and pulverulent masses are concerned. I may likewise 

 observe that in my report to the Government such questions 

 as these concerning and referring solely to the more scientific 

 aspect, must of necessity be very brief, because the larger 

 questions as to the present or ultimate value of any mineral 

 or metalliferous discovery, are of more immediate practical 

 Talue as affecting directly the progress of the community at 

 large. 



In the first place, it appears that the Secretary for Mines 

 obtained the specimens in question from Mr. Grotty, the 

 discoverer of that " Iron Blow." Subsequently, Mr. Johnston, 

 aided by Mr. Ward, the Government Analyst, concluded that 

 the soft purply black and so highly auriferous mineral was 

 the result of decomposition of some of that immense bed or 

 vein of solid j)yrites (iron) filling the greater width of the 

 fissure on its " hanging wall," or about 225 feet out of a total 

 width of 280 feet between walls of that chasm. 



Dismissing all speculations as to whether it has been 

 prudent to base any reliably practical opinion, such as to the 

 question of origin of that valuable deposit, upon the examina- 

 tion of "specimens" only, even though, such was to some 

 degree supported by chemical analyses, it further appears 

 from the late Mr. C. P. Sprent's report that, but a very 

 cursory examination of that deposit, in situ, had been made 

 during that gentleman's and associates' tour from the Ouse 



